精确定位的高带宽新型音圈电机驱动器研究

为了在极高磁道密度（TPI）的硬盘中快速寻道定位、读取数据,研发了一种新型高带宽驱动器组件.该新型高带宽驱动器的音圈电机（VCM）具有独特的音圈结构和磁极（体）排列.在电磁设计中,应用三维有限元分析法（FEA）对一些关键电磁参数及主要结构尺寸进行了优化;预测了系统的动态性能.分析表明,新型音圈电机驱动器产生的电磁力形成了纯力矩,降低了轴承和轴上的反作用力,与传统驱动器相比,更好地抑制了影响伺服带宽的横向准刚性体震动模式（QR模式）,使驱动系统能在高TPI下快速跟踪和精确定位.实验测试了系统的频率响应特性,与理论设计符合得较好.     

柔性基电磁屏蔽材料的研究进展

本文介绍了电磁屏蔽材料的屏蔽原理、电磁屏蔽损耗材料的类型及性能,总结了柔性基电磁屏蔽材料的制备方法及其研究进展。     

Highly Uniform and Stable Transparent Electromagnetic Interference Shielding Film Based on Silver Nanowire–PEDOT:PSS Composite for High Power Microwave Shielding

Electromagnetic interference (EMI) shielding materials, especially ones with excellent shielding effectiveness (SE), high optical transmittance, long-term stability as well as high uniformity, are urgently desired to meet the requirements of many applications. Herein, an extremely transparent, stable and uniform silver nanowire (Ag NW)–poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite film as an EMI shielding material is prepared, which possess excellent shielding capability to both small signal and high power microwaves (HPM). The composite film exhibits SE of 30.5 dB in the frequency range of 1–12 GHz (small signal) and simultaneously has an optical transmittance of 91.0%. The SE continuously increases to 41.4 dB, while the optical transmittance still maintains at 81.1%. The composite film is very uniform, and its SE is almost unchanged even when exposed in air for a year. The SE of this composite film under the excitation of HPM is also thoroughly investigated. The HPM SE is much larger than that of small signal. As the power density of HPM is increased, the SE firstly remains unchanged, then continuously increases, and finally saturates. The SE exceeds 50 dB with the excitation power density of 40 W. More interestingly, the SE is saturated at a fixed HPM power density.     

Synergistic Effect of PVDF-Coated PCL-TCP Scaffolds and Pulsed Electromagnetic Field on Osteogenesis

Bone exhibits piezoelectric properties. Thus, electrical stimulations such as pulsed electromagnetic fields (PEMFs) and stimuli-responsive piezoelectric properties of scaffolds have been investigated separately to evaluate their efficacy in supporting osteogenesis. However, current understanding of cells responding under the combined influence of PEMF and piezoelectric properties in scaffolds is still lacking. Therefore, in this study, we fabricated piezoelectric scaffolds by functionalization of polycaprolactone-tricalcium phosphate (PCL-TCP) films with a polyvinylidene fluoride (PVDF) coating that is self-polarized by a modified breath-figure technique. The osteoinductive properties of these PVDF-coated PCL-TCP films on MC3T3-E1 cells were studied under the stimulation of PEMF. Piezoelectric and ferroelectric characterization demonstrated that scaffolds with piezoelectric coefficient d₃₃ = −1.2 pC/N were obtained at a powder dissolution temperature of 100 °C and coating relative humidity (RH) of 56%. DNA quantification showed that cell proliferation was significantly enhanced by PEMF as low as 0.6 mT and 50 Hz. Hydroxyapatite staining showed that cell mineralization was significantly enhanced by incorporation of PVDF coating. Gene expression study showed that the combination of PEMF and PVDF coating promoted late osteogenic gene expression marker most significantly. Collectively, our results suggest that the synergistic effects of PEMF and piezoelectric scaffolds on osteogenesis provide a promising alternative strategy for electrically augmented osteoinduction. The piezoelectric response of PVDF by PEMF, which could provide mechanical strain, is particularly interesting as it could deliver local mechanical stimulation to osteogenic cells using PEMF.     

宽频带范围下磁场能量收集的匹配网络设计

磁场能量收集技术是电磁环境中分布式传感器实现自供能的有效手段。与工频磁场和射频磁场等单一频率的磁场环境不同,电力变换器中的磁场分布具有宽频率范围特性。为了提高取能模块的功率密度,应尽可能多地在有限体积内收集能量,提出通过采用双级谐振-带通滤波网络。与此同时,基于相同取能线圈,充分对比了不同电流和负载特性下,单级谐振网络和双级谐振-带通网络的输出特性,归纳出双级谐振-带通网络的适用范围。     

电、磁场对金属凝固组织的影响及应用

利用外加物理场凝固细晶技术是目前材料加工领域的研究热点。综述了各种电、磁场对金属凝固组织的影响，并对其主要的机理进行了探讨；并对电、磁场在金属凝固成形中的应用和进一步研究进行了展望。     

变频调速传动系统的电磁兼容分析

在变频调速传动系统中,变频器会产生和受到各种电磁干扰。本文分析了变频调速传动系统的主要电磁干扰源和耦合途径,并阐述了抑制其电磁干扰的措施。     

THEORETICAL INVESTIGATION ON BY-ONLY-CURRENT ELECTROMAGNETIC SEPARATION OF INCLUSION FROM MOLTEN METALS

The electromagnetic field under applied AC and DC current in round and rectangular pipe was systematically investigated, then a concept of "equivalent current density" was proposed for evaluating the inhomogeneous electromagnetic pinch force, and the mono-component removal efficiency and the overall removal efficiency of inclusion were formulated. It is founded that flat pipe is superior to round pipe for the electromagnetic removal of inclusion, and DC current can get a higher removal efficiency than A C current due to absence of skin phenomenon. Under usual condition, a removal efficiency of 52% for 10μm inclusion or more than 92% for 20μm inclusion can be achieved by imposing a current density of 3×106A/m2 in a flat pipe.     

单道自动对接焊应变应力场分析

通过给出模拟单道自动对接焊过程的数学模型，用有元法计算瞬时应变场和应力场并与实测值进行比较，结果证实计算值与实测值基本吻合，表明用数学模拟自动对接焊过程是可行的。     

磁性纤维随机混合媒质等效电磁参数的计算

为计及强散射偶极子间的相互作用,引入参量εh和μh,利用广义多重散射理论及MATLAB计算机软件对在2 GHz～18 GHz频率下的体积占空比为8%的铁纤维随机混合媒质等效磁导率的实验值进行曲线的拟合,导出了耦合系数εh和μh,并在此基础上,对体积占空比分别为30%和20%的铁纤维随机混合媒质等效磁导率进行了计算,计算结果与实验吻合良好.